Discipline: Biological Sciences
Subcategory: Microbiology/Immunology/Virology
Session: 2
Room: Exhibit Hall A
Natalie Melendez-Velador - Seward County Community College
Co-Author(s): Ashlee Herken, Kansas State University, Manhattan, KS; Thomas G. Platt, Kansas State University, Manhattan, KS
Many agrobacteria are plant pathogens that cause crown gall disease in a wide-range of dicotyledonous plants, including several economically important crops. Plants with crown gall disease develop tumors due to the misregulation of key growth hormones and also produce opines, specialized nutrients broken down by pathogenic agrobacteria that are unavailable to most other bacteria. Pathogenic agrobacteria carry a tumor-inducing (Ti) plasmid that encodes most functions required for plant infection and the ability to benefit from opines produced by infected plants. Some related bacteria carry plasmids that encoded opine catabolism functions but not pathogenesis functions. These cheater strains outcompete pathogenic strains in the presence of infected plants. The best characterized cheater is Rhizobium rhizogenes strain K84 which carries a cheater plasmid and produces a bacteriocin that inhibits the growth of agrobacterial pathogens carrying Ti plasmids that cause plants to produce the opines nopaline, nopalinic acid, agrocinopine A, and agrocinopine B. In this study, we aimed to determine whether a sample of biovar 1 agrobacteria produce bacteriocins inhibiting the growth of several pathogenic strains, including strains with whom they co-occur. This work has the potential to lead to the discovery of noval biocontrol agents for crown gall disease. Root samples of common sunflowers, Helianthus annuus, were collected from Konza Prairie. Isolates were grown on semi-selective media that supports the growth of biovar 1 agrobacteria but excludes the growth of most fungi and bacteria present a in the microbial communities on plant roots. We used an inhibition assay to determine if agrobacterial isolates produce bacteriocins interfering with the growth of Agrobacterium tumefaciens strains C58, 15955, and K203. Each of these strains are pathogenic with C58 containing a nopaline-type Ti plasmid, 15955 containing an octopine-type Ti plasmid, and K203 being isolated from the same plant as some of the isolates being tested. Experiments are ongoing but preliminary results indicate that several of the environmental isolates inhibit the growth of C58 but not 15955 or K203. This strain-specific inhibition is consistent with prior work with pathogenic agrobacteria, however we see no evidence for bacteriocin mediated interference competition among co-occurring strains. Future work will aim to determine the mechanisms mediating strain-specific C58 inhibition, including the possibility that inhibition depends on Ti plasmid encoded functions.
Funder Acknowledgement(s): KS-LSAMP supported by National Science Foundation (NSF) grant no. 1305059; Kansas EPSCoR - grant no. OIA-1656006
Faculty Advisor: Thomas G. Platt, tgplatt@ksu.edu
Role: I grew the agrobacteria strains and carried out the inhibition assay that determined whether the strains produced bacteriocins.